The statements in this section merely provide background information related to the present disclosure and may not constitute prior art. In conventional combustion engines, the walls delimiting combustion chambers are of a cylindrical shape and closed on one end with a cylinder head. A piston is moveably guided through the other end into the cylinder. Internal combustion engines have 4 basic steps: (1) intake; (2) compression; (3) combustion and expansion; and (4) exhaust. During the intake step, combustible mixtures are injected into the combustion chamber. This mixture is placed under pressure by the compression of the piston into the cylinder. The mixture is then ignited and burnt. The hot combustion products ultimately expand, forcing the piston to move in the opposite direction and causing the transfer of energy to mechanical components that are coupled or connected to the piston, such as a crankshaft. The cooled combustion products are finally exhausted and the combustion cycle restarts. Typical combustion engines operate according to this principle may function in two cycles or four cycles, such as in Otto and diesel engines.
There exists a continuing issue related to the relatively low efficiency exhibited by conventional combustion engines. Engine efficiency is usually defined by comparing the theoretical chemical energy in the fuels against the useful energy abstracted from the fuels in the form of the kinetic energy transferred through the engine. Although the thermodynamic limit for abstracting energy from a typical fuel is about 80%, typical combustion engines exhibit an average efficiency of only about 20-40%. Therefore, there remains substantial room for improvement in efficiency over conventional internal combustion engines.